processor_content_modifier: add support for OTel Logs Resource and Scopes

[edsiper]

The following patch extends the processor to allow to modify the resources and scopes of Logs generated by an OpenTelemetry source.

The following new contexts are supported:

• otel_resource_attributes: alter resource attributes
• otel_scope_name: manipulate the scope name
• otel_scope_version: manipulate the scope version
• otel_scope_attributes: alter the scope attributes

example: fluent-bit.yaml

service:
  flush: 1
  log_level: info
  http_server: on
  http_port: ${FLUENT_BIT_HTTP_MONITORING_PORT}

  pipeline:
    inputs:
      - name: opentelemetry
        port: ${FLUENT_BIT_TEST_LISTENER_PORT}
        processors:
          logs:
            - name: content_modifier
              context: otel_resource_attributes
              action: upsert
              key: "new_attr"
              value: "my_val"

            - name: content_modifier
              context: otel_resource_attributes
              action: delete
              key: "service.name"

            - name: content_modifier
              context: otel_scope_attributes
              action: upsert
              key: "my_new_scope_attr"
              value: "123"

            - name: content_modifier
              context: otel_scope_name
              action: upsert
              value: "new scope name"

            - name: content_modifier
              context: otel_scope_version
              action: upsert
              value: "3.1.0"

  outputs:
    - name: stdout
      match: '*'

    - name: opentelemetry
      match: '*'
      host: 127.0.0.1
      port: ${TEST_SUITE_HTTP_PORT}

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Testing
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• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

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• Run local packaging test showing all targets (including any new ones) build.
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Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.